Selecting radio frequency channels for carrier aggregation in an unlicensed radio frequency spectrum band

ABSTRACT

A base station may obtain channel usage information identifying usage of one or more unlicensed radio frequency (RF) spectrum bands. The base station may select a selected band, of the one or more unlicensed RF spectrum bands, based on the channel usage information. The base station may select one or more RF channels, of multiple RF channels included in the selected band, based on a congestion value of the selected band. The congestion value may be determined based on values of the channel usage information corresponding to the selected band. The selected RF channel may include an impaired RF channel that may not permit full bandwidth utilization due to constraints. The base station may communicate with user equipment via the one or more RF channels of the selected band.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/978,097, filed Dec. 22, 2015, the disclosure of which is incorporatedherein by reference.

BACKGROUND

Wireless devices may communicate over an unlicensed radio frequency (RF)spectrum band using one or more radio access technologies, such as awireless local area network (WLAN) radio access technology, a long termevolution (LTE) radio access technology, or the like. An unlicensed RFspectrum band may refer to an RF spectrum band that is open for shareduse by any device that complies with regulatory agency rules forcommunicating via the RF spectrum band. In contrast with most licensedRF spectrum band usage, users of unlicensed RF spectrum bands do nottypically have regulatory protection against radio interference fromdevices of other users. In other words, devices that use the unlicensedRF spectrum band must typically accept any radio interference caused byother devices that use the unlicensed RF spectrum band.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrams of an overview of an example implementationdescribed herein;

FIG. 2 is a diagram of an example environment in which systems and/ormethods, described herein, may be implemented;

FIG. 3 is a diagram of example components of one or more devices of FIG.2; and

FIG. 4 is a flow chart of an example process for selecting radiofrequency channels for carrier aggregation in an unlicensed radiofrequency spectrum band.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description of example implementations refers tothe accompanying drawings. The same reference numbers in differentdrawings may identify the same or similar elements.

A wireless device, such as a user equipment (UE), may be capable ofcommunicating using licensed radio frequency (RF) spectrum bands andunlicensed RF spectrum bands. The licensed RF spectrum bands may belicensed for use by a particular network operator, while the unlicensedRF spectrum bands may be open for shared use by any device that complieswith regulatory agency rules for communicating via the unlicensed RFspectrum bands. Network operators may wish to utilize unlicensed RFspectrum to reduce network congestion, increase throughput, or the like,by aggregating the unlicensed RF spectrum band with the licensed RFspectrum band (e.g., using a carrier aggregation system, based on alicense-assisted access (LAA) technology, based on aLong-Term-Evolution-Advanced (LTE-A) technology, based on an LTE inunlicensed spectrum (LTE-U) protocol, etc.).

An RF spectrum band (e.g., a licensed RF spectrum band, an unlicensed RFspectrum band, etc.) may be composed of one or more RF channels (alsoreferred to as “carriers” or “carrier frequencies”). Some RF channelsmay be used by wireless devices more than other RF channels (e.g., basedon technical considerations, based on limitations imposed by regulatoryagency rules, etc.). As one possible example, RF channel 32 of theUnlicensed National Information Infrastructure (U-NII) Low RF spectrumband (e.g., U-NII-1) may be used less than other RF channels of theU-NII-1 band, and therefore may be less congested than the other RFchannels (e.g., as measured by bandwidth utilization, a quantity ofallocated time slots for time division multiplexing, etc.).

RF channel 32 may be used less than the other RF channels of the U-NII-1band based on wireless devices that can transmit on RF channel 32sometimes being incapable of satisfying limitations imposed byregulatory agency rules regarding out-of-channel transmission values.For example, consumer-grade wireless local area network (WLAN) routers,or the like, may use components that are not sufficiently precise tosatisfy out-of-channel transmission limitations on RF channel 32. Forthis reason, RF channel 32 may be less heavily utilized, and thereforeless congested, than other RF channels of the U-NII-1 band.

Implementations described herein enable a base station to select one ormore RF channels, of one or more unlicensed RF spectrum bands, via whichto communicate with wireless devices. The base station may select theone or more RF channels based on congestion in the one or moreunlicensed RF spectrum bands to improve throughput, reduce interference,and the like. In some cases, the base station may select “impaired” RFchannels that are historically less congested than other RF channels dueto the difficulties in utilizing such channels within requiredconstraints (e.g., RF channel 32 of the U-NII-1 band, RF channel 165 ofa U-NII-3 band as described in more detail below, etc.), which reducesinterference from other wireless devices operating in a correspondingunlicensed RF spectrum band. In this way, the base station reducesnetwork congestion and interference and improves throughput.

FIGS. 1A and 1B are diagrams of an overview of an example implementation100 described herein. As shown in FIG. 1A, and by reference number 105,wireless devices (e.g., UEs, access points, WLAN routers, etc.) mayoperate in one or more unlicensed RF spectrum bands, such as a U-NIIradio band. The U-NII radio band may include, for example, a U-NII Lowband, or U-NII-1, a U-NII Mid band, or U-NII-2, a U-NII Worldwide band,or U-NII-2e, and/or a U-NII Upper band, or U-NII-3, as described in moredetail elsewhere herein.

As the wireless devices operate, the wireless devices may communicatevia one or more RF channels of the one or more unlicensed RF spectrumbands, which may create interference and congestion in the one or moreRF channels. In some cases, the wireless devices may tend not to operatein a particular impaired RF channel (e.g., RF channel 32 of the U-NII-1band) based on configurations of the wireless devices and/or based onlimitations imposed by regulatory agency rules regarding out-of-channeltransmission, as described in more detail above.

As shown by reference number 110, a base station may measure channelusage in the one or more unlicensed RF spectrum bands (e.g.,periodically, on demand, etc.). For example, the base station may obtainchannel usage information identifying bandwidth utilization values,interference levels, or the like, of RF channels included in the one ormore unlicensed RF spectrum bands. A bandwidth utilization value mayidentify a ratio of allocated bandwidth in a particular RF channel tototal bandwidth associated with the particular RF channel, or the like.An interference level may measure a quantity, strength, and/or qualityof signals received in the particular RF channel.

As shown by reference number 115, the base station may obtain channelusage information relating to the U-NII-1 band. Here, the channel usageinformation indicates that RF channel 32 is associated with no usage,that RF channels 36 and 48 are associated with low usage (e.g., based onbandwidth utilization values, interference levels, quantities of UEs,etc. associated with RF channels 36 and/or 48), and that RF channels 40and 44 are associated with moderate usage.

As shown by reference number 120, the base station may obtain channelusage information relating to the U-NII-3 band. Here, the channel usageinformation indicates that RF channels 149, 157, 161, and 165 areassociated with high usage, and that RF channel 153 is associated withlow usage. As shown by reference number 125, based on the channel usageinformation, the base station may select the U-NII-1 band. For example,the base station may determine scores for the U-NII-1 band and theU-NII-3 band based on the channel usage information, and may select theU-NII-1 band based on comparing the scores (e.g., based on a score forthe U-NII-1 band indicating that the U-NII-1 band is less congested thanthe U-NII-3 band), as described in more detail elsewhere herein.

The base station may select the U-NII-1 band to provide a secondaryserving carrier (e.g., based on a license-assisted access technology, anLTE-Advanced technology, etc.) to UEs that are associated with the basestation. In this case, the base station may use a licensed RF spectrumband for a primary serving carrier (e.g., for uplink information, as ananchor for UEs, etc.), and may use the U-NII-1 band for a secondaryserving carrier (e.g., for downlink information). In other cases, thebase station may provide uplink information and downlink information viathe U-NII-1 band. That is, the base station may use the U-NII-1 band toprovide a primary serving carrier for the UEs.

As shown in FIG. 1B, and by reference number 130, the base station mayallocate RF channels of the U-NII-1 band based on a congestion value forthe U-NII-1 band (e.g., an average value of channel usage informationfor RF channels associated with the U-NII-1 band, a weighted averagevalue of the channel usage information, a median value of the channelusage information, one or more effective bandwidths of RF channelsassociated with the U-NII-1 band, etc.). As shown, the base station mayallocate the RF channels based on a rule. Here, the rule indicates thatRF channels 36 and 40 are to be selected when the congestion value islow, that RF channels 32 and 36 are to be selected when the congestionvalue is moderate, and that RF channel 32 is to be selected when thecongestion value is high (e.g., when other RF channels of the U-NII-1band are likely to be more congested than RF channel 32).

As shown by reference number 135, the base station determines that thecongestion value for the U-NII-1 band is moderate (e.g., based onchannel usage information for the RF channels included in the U-NII-1band). As shown by reference number 140, the base station allocates(e.g., selects) RF channels 32 and 36 to provide a secondary servingcarrier in a carrier aggregation operation. For example, the basestation may use RF channels of a licensed RF spectrum band to provide aprimary serving carrier, and may use RF channels 32 and 36 to provide asecondary serving carrier based on a carrier aggregation operation.

As shown by reference number 145, the base station provides information,to UEs, indicating that RF channels 32 and 36 are available for use toprovide secondary serving carriers. In some cases, the base station mayprovide information identifying a particular bandwidth and/or frequencyassociated with RF channels 32 and/or 36, time slots associated with RFchannels 32 and/or 36, or the like.

In this way, the base station selects an unlicensed RF spectrum band andallocates RF channels of the selected band based on congestion in theselected band. In some implementations, when a selected band isassociated with high congestion (e.g., a congestion value that satisfiesa threshold), the base station may allocate an impaired RF channel thatis typically associated with a lower congestion value (e.g., based onwireless devices that use the selected band not being configured totransmit in the particular RF channel), which reduces congestion andinterference.

As indicated above, FIGS. 1A and 1B are provided merely as an example.Other examples are possible and may differ from what was described withregard to FIGS. 1A and 1B.

FIG. 2 is a diagram of an example environment 200 in which systemsand/or methods, described herein, may be implemented. As shown in FIG.2, environment 200 may include a user equipment (UE) 210, a base station220, and a network 230. Devices of environment 200 may interconnect viawired connections, wireless connections, or a combination of wired andwireless connections.

UE 210 may include one or more devices capable of connecting to anetwork via base station 220 and an unlicensed RF spectrum band. Forexample, UE 210 may include a communication device, such as a mobilephone (e.g., a smart phone, a radiotelephone, etc.), a laptop computer,a tablet computer, a gaming device, a wearable communication device(e.g., a smart wristwatch, a pair of smart eyeglasses, etc.), amachine-to-machine communication device, or a similar type of device.

Base station 220 may include one or more devices capable of transferringtraffic, such as audio, video, text, and/or other traffic, destined forand/or received from UE 210. In some implementations, base station 220may communicate wirelessly with UE 210 using one or more wirelesscommunication protocols, such as, for example, the Institute ofElectrical and Electronics Engineers (IEEE) 802.11 protocol (e.g.,Wi-Fi), a long term evolution in unlicensed spectrum (LTE-U) protocol,or the like. For example, base station 220 may include a base station ofa radio access network, a node B, an evolved node B, a large cell basestation (e.g., a base station of a macrocell), a small cell base station(e.g., a base station of a microcell, a picocell, a femtocell, etc.), orthe like.

Base station 220 may provide UE 210 with access to an unlicensed RFspectrum band to permit UE 210 to communicate using the unlicensed RFspectrum band. In some implementations, the unlicensed RF spectrum bandmay be used by base station 220 and UE 210 registered with an operatornetwork (e.g., a cellular network, network 230, etc.) for LTEcommunications and/or LTE-Advanced (LTE-A) communications, and by WLANaccess points and WLAN stations of a WLAN network for WLANcommunications. The unlicensed RF spectrum band may be used by theoperator network in combination with, or independent from, a licensed RFspectrum band. In some implementations, the unlicensed RF spectrum bandmay be an RF spectrum band for which UE 210 may need to contend foraccess because the RF spectrum band is available, at least in part, forunlicensed use, such as WLAN use.

As an example, the unlicensed RF spectrum band may include one or moreradio frequencies (e.g., one or more radio frequency spectrum bands)included in the radio spectrum (e.g., the portion of the electromagneticspectrum corresponding to radio frequencies, or frequencies lower thanapproximately 300 gigahertz (GHz)). In some implementations, theunlicensed RF spectrum band may include one or more RF spectrum bandsthat are open for shared use by any device that complies with regulatoryagency rules (e.g., associated with a particular country) forcommunicating via the one or more RF spectrum bands. For example, theunlicensed RF spectrum band may include one or more radio frequenciesbetween approximately 5 GHz and approximately 6 GHz. As a more specificexample, the unlicensed RF spectrum band may include one or more radiofrequencies between approximately 5.15 GHz and approximately 5.825 GHz.

As another example, the unlicensed RF spectrum band may include one ormore RF spectrum bands defined by the United States FederalCommunications Commission (FCC) as the Unlicensed National InformationInfrastructure (U-NII) radio band. The U-NII radio band may include, forexample, a first RF spectrum band between approximately 5.15 GHz andapproximately 5.25 GHz (e.g., the U-NII Low band, or U-NII-1), a secondRF spectrum band between approximately 5.25 GHz and approximately 5.35GHz (e.g., the U-NII Mid band, or U-NII-2a), a third RF spectrum bandbetween approximately 5.47 GHz and approximately 5.725 GHz (e.g., theU-NII Worldwide band, or U-NII-2c), and/or a fourth RF spectrum bandbetween approximately 5.725 GHz and approximately 5.825 GHz (e.g., theU-NII Upper band, or U-NII-3).

The unlicensed RF spectrum band may be divided into RF channels viawhich RF communications may be transmitted. For example, the unlicensedRF spectrum band may include one or more channels of approximately 20MHz bandwidth. UE 210 may communicate via an RF channel included in theunlicensed RF spectrum band. For example, UE 210 may communicate via anRF channel using a WLAN radio access technology, an LTE radio accesstechnology, or the like.

Network 230 may include one or more wired and/or wireless networks. Forexample, network 230 may include a radio access network, a cellularnetwork (e.g., an LTE network, a third generation (3G) network, a fourthgeneration (4G) network, a fifth generation (5G) network, a codedivision multiple access (CDMA) network, etc.), a public land mobilenetwork (PLMN), a local area network (LAN), a wide area network (WAN), ametropolitan area network (MAN), a telephone network (e.g., the PublicSwitched Telephone Network (PSTN)), a private network, an ad hocnetwork, an intranet, the Internet, a fiber optic-based network, a cloudcomputing network, or the like, and/or a combination of these or othertypes of networks. In some implementations, network 230 may include acore network of a cellular network operator.

The number and arrangement of devices and networks shown in FIG. 2 areprovided as an example. In practice, there may be additional devicesand/or networks, fewer devices and/or networks, different devices and/ornetworks, or differently arranged devices and/or networks than thoseshown in FIG. 2. Furthermore, two or more devices shown in FIG. 2 may beimplemented within a single device, or a single device shown in FIG. 2may be implemented as multiple, distributed devices. Additionally, oralternatively, a set of devices (e.g., one or more devices) ofenvironment 200 may perform one or more functions described as beingperformed by another set of devices of environment 200.

FIG. 3 is a diagram of example components of a device 300. Device 300may correspond to UE 210 and/or base station 220. In someimplementations, UE 210 and/or base station 220 may include one or moredevices 300 and/or one or more components of device 300. As shown inFIG. 3, device 300 may include a bus 310, a processor 320, a memory 330,a storage component 340, an input component 350, an output component360, and a communication interface 370.

Bus 310 may include a component that permits communication among thecomponents of device 300. Processor 320 is implemented in hardware,firmware, or a combination of hardware and software. Processor 320 mayinclude a processor (e.g., a central processing unit (CPU), a graphicsprocessing unit (GPU), an accelerated processing unit (APU), etc.), amicroprocessor, and/or any processing component (e.g., afield-programmable gate array (FPGA), an application-specific integratedcircuit (ASIC), etc.) that interprets and/or executes instructions. Insome implementations, processor 320 may include one or more processorscapable of being programmed to perform a function. Memory 330 mayinclude a random access memory (RAM), a read only memory (ROM), and/oranother type of dynamic or static storage device (e.g., a flash memory,a magnetic memory, an optical memory, etc.) that stores informationand/or instructions for use by processor 320.

Storage component 340 may store information and/or software related tothe operation and use of device 300. For example, storage component 340may include a hard disk (e.g., a magnetic disk, an optical disk, amagneto-optic disk, a solid state disk, etc.), a compact disc (CD), adigital versatile disc (DVD), a floppy disk, a cartridge, a magnetictape, and/or another type of computer-readable medium, along with acorresponding drive.

Input component 350 may include a component that permits device 300 toreceive information, such as via user input (e.g., a touch screendisplay, a keyboard, a keypad, a mouse, a button, a switch, amicrophone, etc.). Additionally, or alternatively, input component 350may include a sensor for sensing information (e.g., a global positioningsystem (GPS) component, an accelerometer, a gyroscope, an actuator,etc.). Output component 360 may include a component that provides outputinformation from device 300 (e.g., a display, a speaker, one or morelight-emitting diodes (LEDs), etc.).

Communication interface 370 may include a transceiver-like component(e.g., a transceiver, a separate receiver and transmitter, etc.) thatenables device 300 to communicate with other devices, such as via awired connection, a wireless connection, or a combination of wired andwireless connections. Communication interface 370 may permit device 300to receive information from another device and/or provide information toanother device. For example, communication interface 370 may include anEthernet interface, an optical interface, a coaxial interface, aninfrared interface, a radio frequency (RF) interface, a universal serialbus (USB) interface, a WLAN interface, a cellular network interface, orthe like.

Device 300 may perform one or more processes described herein. Device300 may perform these processes in response to processor 320 executingsoftware instructions stored by a non-transitory computer-readablemedium, such as memory 330 and/or storage component 340. Acomputer-readable medium is defined herein as a non-transitory memorydevice. A memory device includes memory space within a single physicalstorage device or memory space spread across multiple physical storagedevices.

Software instructions may be read into memory 330 and/or storagecomponent 340 from another computer-readable medium or from anotherdevice via communication interface 370. When executed, softwareinstructions stored in memory 330 and/or storage component 340 may causeprocessor 320 to perform one or more processes described herein.Additionally, or alternatively, hardwired circuitry may be used in placeof or in combination with software instructions to perform one or moreprocesses described herein. Thus, implementations described herein arenot limited to any specific combination of hardware circuitry andsoftware.

The number and arrangement of components shown in FIG. 3 are provided asan example. In practice, device 300 may include additional components,fewer components, different components, or differently arrangedcomponents than those shown in FIG. 3. Additionally, or alternatively, aset of components (e.g., one or more components) of device 300 mayperform one or more functions described as being performed by anotherset of components of device 300.

FIG. 4 is a flow chart of an example process 400 for selecting radiofrequency channels for carrier aggregation in an unlicensed radiofrequency spectrum band. In some implementations, one or more processblocks of FIG. 4 may be performed by base station 220. In someimplementations, one or more process blocks of FIG. 4 may be performedby another device or a group of devices separate from or including basestation 220, such as UE 210.

As shown in FIG. 4, process 400 may include obtaining channel usageinformation identifying usage of radio frequency channels of one or moreunlicensed radio frequency spectrum bands (block 410). For example, basestation 220 may transmit and/or receive network traffic via one or moreRF spectrum bands. In some implementations, base station 220 maytransmit and/or receive network traffic via a licensed RF spectrum bandand/or a licensed RF channel. For example, a particular UE 210 may beassociated with a particular operator network, and the particular UE 210may communicate with base station 220 on an RF spectrum band and/or anRF channel that is licensed to the particular operator network (e.g., bya government agency). Additionally, or alternatively, base station 220may communicate with the particular UE 210 on an RF spectrum band and/oran RF channel that is not licensed to the particular operator network(e.g., using an LTE signal, a WLAN signal, etc.).

Base station 220 may obtain channel usage information relating to usageof RF channels of one or more unlicensed RF spectrum bands. The one ormore unlicensed RF spectrum bands may include, for example, the U-NII-1band, the U-NII-2a band, the U-NII-2c band, the U-NII-3 band, when inthe United States of America, or another unlicensed RF spectrum band. Insome implementations, the channel usage information may includeinformation identifying congestion values of RF channels included in anunlicensed RF spectrum band. For example, the channel usage informationfor an RF channel may identify a quantity of time slots allocated on theRF channel, may identify a ratio of available time slots on the RFchannel to total time slots on the RF channel, may identify a quantityof data transmitted on the RF channel, may identify a signal strength ofRF signals received by base station 220 on the RF channel (e.g., RFsignals originating from UE 210, originating from a WLAN access point,etc.), may identify a bandwidth utilization value of the RF channel(e.g., based on a ratio of available bandwidth on the RF channel tototal bandwidth on the RF channel, etc.), an interference levelassociated with the RF channel, or the like.

In some implementations, base station 220 may obtain the channel usageinformation periodically (e.g., once per second, once per minute, onceper hour, once per day, etc.), based on an instruction from a user,based on an instruction from another device, based on establishing asession with UE 210, or the like. In some implementations, base station220 may obtain the channel usage information based on a congestion levelof a licensed RF channel and/or a licensed RF spectrum band. Forexample, base station 220 may determine that a value associated with alicensed RF spectrum band satisfies a threshold (e.g., a thresholdcongestion level, a threshold bandwidth utilization value, a thresholdinterference level, a threshold quantity of UEs 210 associated with thelicensed RF spectrum band, etc.). Based on determining that the licensedRF spectrum band satisfies the threshold, base station 220 may obtainthe channel usage information to allocate unlicensed RF spectrumbandwidth to UEs 210 associated with base station 220 (e.g., in additionto the licensed RF spectrum band, in place of the licensed RF spectrumband, etc.). In this way, base station 220 reduces congestion on thelicensed RF spectrum, which improves cellular network operation andincreases throughput of the cellular network.

As further shown in FIG. 4, process 400 may include selecting a selectedband, of the one or more unlicensed radio frequency spectrum bands,based on the channel usage information (block 420). For example, basestation 220 may select a selected band, of the one or more unlicensed RFspectrum bands, based on the channel usage information. In someimplementations, base station 220 may select the selected band based oncongestion values of the one or more unlicensed RF spectrum bands. Forexample, base station 220 may select the selected band based on theselected band being less congested than other unlicensed RF spectrumbands of the one or more unlicensed RF spectrum bands.

As one possible example, assume that base station 220 obtains channelusage information for two unlicensed RF spectrum bands: the U-NII-1 bandand the U-NII-3 band. Base station 220 may select the selected band,from the U-NII-1 band and the U-NII-3 band, based on the belowequations:Selected band=max(F1,F2), whereF1=∝₃₂ U ₃₂+∝₃₆ W ₃₆+∝₄₀ W ₄₀+∝₄₄ W ₄₄+∝₄₈ W ₄₈, andF2=∝₁₄₉ W ₁₄₉+∝₁₅₃ W ₁₅₃+∝₁₅₇ W ₁₅₇+∝₁₆₁ W ₁₆₁+∝₁₆₅ W ₁₆₅.

In the above equations, F1 corresponds to the U-NII-1 band, and F2corresponds to the U-NII-3 band. F1 and F2 are scores that are assignedto the U-NII-1 band and the U-NII-3 band, respectively, based on valuesof U, W, and α. U, W, and α are described in more detail below. A highervalue of F1 or F2 may indicate that a corresponding unlicensed RFspectrum is less congested than a lower value of F1 or F2. For example,when F1 is equal to 0.75, the U-NII-1 band may be less congested thanwhen F1 is equal to 0.25. As shown, base station 220 may select theselected band based on a maximum value of F1 and F2. For example, if F1is greater than F2, base station 220 may select the U-NII-1 band, and ifF2 is greater than F1, base station 220 may select the U-NII-3 band.

W may correspond to weights that may be assigned to RF channels based ona ranking of the RF channels with regard to congestion of the RFchannels. For example, a more congested RF channel may be ranked below aless congested RF channel, and may therefore be assigned a lower Wvalue. Here, W₃₂ corresponds to RF channel 32 of the U-NII-1 band, W₁₄₉corresponds to RF channel 149 of the U-NII-3 band, and so on. In someimplementations, W may include values between 0 and 1 (e.g., may benormalized), or may include a different range of values. In someimplementations, values of W may be defined by a network operatorassociated with base station 220. For example, the network operator maydefine a value of W of 1 for a highest-ranking RF channel, a value of Wof 0.5 for a middle-ranking RF channel, a value of W of 0 for alowest-ranking RF channel, or the like.

U may identify a weight that may be assigned to an impaired RF channel,identified by a subscript of U, that is historically associated withless congestion than other RF channels of a particular band. Here, U₃₂is assigned to RF channel 32 of the U-NII-1 band. In this example, avalue of U₃₂ may be different (e.g., higher, etc.) than values of W forthe U-NII-1 band (e.g., a maximum value of W₃₆ through W₄₈, an averagevalue of W₃₆ through W₄₈, etc.). In this way, base station 220emphasizes RF channel 32 in the selection process based on RF channel 32being an impaired RF channel that historically being associated withless congestion than other RF channels in the unlicensed RF spectrum, asdescribed in more detail elsewhere herein. In some cases, base station220 may assign a value of U for an impaired RF channel in anotherunlicensed RF spectrum band. As one possible example, base station 220may assign a value of U₁₆₅ for RF channel 165 in the U-NII-3 band (e.g.,based on RF channel 165 historically being associated with less usagethan other RF channels of the U-NII-3 band).

In some implementations, base station 220 may assign a particular valueof U based on an effective bandwidth that base station 220 is capable oftransmitting using the impaired RF channel. An effective bandwidth mayidentify a particular bandwidth that base station 220 is capable ofusing (e.g., based on components/configuration of base station 220),without violating the constraints that apply to the impaired RF channel(e.g., agency rules regarding out-of-band emissions, power levels,etc.). For example, in some implementations, RF channel 32 may becentered at 5,160 MHz, and may include a range of 20 MHz of bandwidth(e.g., from 5,150 MHz to 5,170 MHz). Some base stations 220 may beincapable of transmitting on the full range of bandwidth of RF channel32 (e.g., based on regulations limiting out-of-channel transmissions).For example, to ensure that out-of-channel transmissions do not violatea limitation, some base stations 220 may need to transmit on 15 MHz ofRF channel 32, 10 MHz of RF channel 32, or the like. Such base stations220 may assign a value of U₃₂ that is lower than a value of U₃₂ that maybe assigned by base station 220 that can transmit on the full range ofRF channel 32. In this way, base station 220 assigns a lower weight toRF channel 32 in a situation where base station 220 can utilize lessthan all of a bandwidth of RF channel 32, which improves accuracy of thechannel selection process.

α may identify a congestion level and/or a utilization level of acorresponding RF channel that is identified by a subscript of α. Here,α₃₂ corresponds to RF channel 32 of the U-NII-1 band, α₁₄₉ correspondsto RF channel 149 of the U-NII-3 band, and so on. Base station 220 maydetermine values of α for RF channels based on channel usage informationcorresponding to the RF channels. For example, an RF channel that isfully utilized (e.g., based on all frequency resources of the RF channelbeing allotted to operator networks and/or UEs 210, based on all timeresources of the RF channel being allotted to operator networks and/orUEs 210, etc.) may be associated with a lowest possible value of α(e.g., 0, etc.), and an RF channel that is completely un-utilized (e.g.,based on no frequency resources of the RF channel being allotted, basedon no time resources of the RF channel being allotted, etc.) may beassociated with a highest possible value of α (e.g., 1, etc.). In someimplementations, α may be associated with a different range of values.

In some implementations, base station 220 may determine a particularscore based on historical channel usage information. For example, basestation 220 may obtain channel usage information periodically, and maystore the channel usage information as historical channel usageinformation. Base station 220 may determine values of W, U, and/or αbased on the historical channel usage information. For example, basestation 220 may use an average value of multiple, different channelusage information values for an RF channel, may use a weighted averagevalue (e.g., based on more recent channel usage values being assigned ahigher weight than less recent channel usage values, based on mostrecently obtained channel usage information being assigned a higherweight than less recently obtained channel usage information, etc.) ofthe multiple, different channel usage information values, may discardoutliers of the multiple, different channel usage information values,may compare the historical channel usage information to most recentlyobtained channel usage information to determine whether the channelusage information for an RF channel has changed, or the like.

In some implementations, base station 220 may not collect channel usageinformation for a particular RF channel. For example, for impaired RFchannels (e.g., RF channel 32 of the U-NII-1 band, RF channel 165 of theU-NII-3 band, etc.), base station 220 may not collect channel usageinformation for the RF channel, which conserves processor resources ofbase station 220. In some implementations, base station 220 may collectchannel usage information for impaired RF channels less frequently thanfor the other RF channels. For example, base station 220 may collectchannel usage information for the other RF channels periodically, andmay collect channel usage information for impaired RF channels based ondetermining that a licensed RF spectrum band is associated with aparticular congestion level. In this way, base station 220 conservesprocessor resources.

In some implementations, base station 220 may determine scores based ona model. For example, the model may receive channel usage informationfor an unlicensed RF spectrum band as input, and may output a scorebased on the channel usage information. In some implementations, basestation 220 may train the model based on an algorithm (e.g., a machinelearning algorithm, etc.). For example, base station 220 may input, tothe algorithm, a training set that includes known channel usageinformation and known scores corresponding to the known channel usageinformation. Based on the algorithm, base station 220 may train themodel to determine a relationship between the known channel usageinformation and the known scores. After training the model, base station220 may input, to the model, channel usage information for a particularunlicensed RF spectrum band, and the model may output a score for theparticular unlicensed RF spectrum band. In this way, base station 220conserves processor resources and organizational resources that mayotherwise be used to provide the model (e.g., manually), and improvesaccuracy of the scores.

In some implementations, base station 220 may update the model. Forexample, base station 220 may input particular channel usage informationto the model, and the model may output a score corresponding to theparticular channel usage information. Base station 220 may modify thescore, and may input the particular channel usage information and thescore as modified to the algorithm (e.g., the machine learningalgorithm). Based on the algorithm, base station 220 may update themodel to cause the model to output the score, as modified, based on theparticular channel usage information. Additionally, or alternatively,base station 220 may provide an updated training set that includes newknown channel usage information and new known scores, and may update themodel based on the algorithm and based on the updated training set. Inthis way, base station 220 trains and updates the predictive model,which improves accuracy of the scoring process.

In some implementations, base station 220 may determine that aparticular RF channel is historically associated with less usage thanother RF channels in a particular RF spectrum band. For example, basestation 220 may store historical channel usage information for theparticular RF spectrum band, and may determine, based on the channelusage information, that the particular RF channel is associated withless usage (e.g., a lower congestion value, a lower bandwidthutilization value, etc.) than the other RF channels. In such a case,base station 220 may assign a particular weight to the particular RFchannel (e.g., using a value of U, rather than a value of W, asdescribed in more detail with regard to RF channel 32, above) whendetermining scores for the particular RF spectrum band. In this way,base station 220 identifies RF channels that are associated with lesscongestion than other RF channels, which permits base station 220 toallocate resources of the identified RF channels for UEs 210, therebyimproving network throughput and reducing congestion of other RFchannels.

As further shown in FIG. 4, process 400 may include selecting one ormore selected radio frequency channels, of the selected band, based oncongestion of the selected band (block 430). For example, base station220 may select one or more selected RF channels, of RF channelsassociated with the selected band, based on a congestion level of theselected band. In some implementations, base station 220 may select asingle RF channel, and may communicate with UEs 210 via the single RFchannel.

In some implementations, base station 220 may select multiple, differentRF channels (e.g., consecutive RF channels based on frequencies of theRF channels, non-consecutive RF channels, etc.), and may communicatewith UEs 210 via the multiple, different RF channels. In someimplementations, base station 220 may select one or more first RFchannels for uplink transmissions from UE 210, and may select one ormore second RF channels for downlink transmissions to UE 210, which mayimprove throughput of the uplink transmissions and/or the downlinktransmissions.

In some implementations, base station 220 may select an RF channel basedon a congestion level of an unlicensed RF spectrum band that includesthe RF channel. For example, base station 220 may store a rule thatcorrelates congestion levels of an unlicensed RF spectrum band (e.g.,based on channel usage information associated with the unlicensed RFspectrum band) with one or more corresponding RF channels to beselected. In some implementations, base station 220 may determine thecongestion level based on a bandwidth utilization value (e.g., based ona ratio of utilized bandwidth for an unlicensed RF spectrum band tototal bandwidth for the unlicensed RF spectrum band, based on a ratio ofunutilized bandwidth for an unlicensed RF spectrum band to totalbandwidth for the unlicensed RF spectrum band, etc.), an interferencevalue, a quantity of UEs 210 associated with the unlicensed RF spectrumband, a WLAN signal strength associated with the unlicensed RF spectrumband, or the like.

In some implementations, base station 220 may allocate resources of theselected band and/or one or more selected RF channels in the timedomain. For example, base station 220 may allocate (e.g., queue)downlink traffic for transmission to UEs 210, and/or may transmitdownlink traffic to UEs 210, in different time slots or sets of timeslots for different RF channels. As an example, base station 220 maycause downlink traffic to be provided via a particular RF channel and ina first time slot, and may cause transmission of the downlink trafficvia the particular RF channel to cease in a second time slot (e.g., topermit other devices that use the particular RF channel to use theparticular RF channel). In this way, base station 220 reducesinterference and increases throughput.

As an example, assume that RF channel 32, of the U-NII-1 band, isassociated with historically lower congestion levels than other RFchannels of the U-NII-1 band (e.g., RF channels 36 through 48), asdescribed in more detail elsewhere herein. Assume further that basestation 220 selects the U-NII-1 band as the selected band. Assume thatbase station 220 can use 15 MHz of RF channel 32 (e.g., based onregulatory requirements limiting out-of-band transmissions, and based onconfiguration information of base station 220 identifying RF channel 32and the bandwidth of 15 MHz), and assume that base station 220 can use20 MHz of the other RF channels of the U-NII-1 band.

In a situation where the U-NII-1 band is associated with a relativelyhigh congestion value (e.g., a bandwidth utilization value of, forexample, approximately 50% to approximately 100%, etc.), base station220 may determine (e.g., based on a rule, etc.) to use RF channel 32.Base station 220 may communicate with UEs 210 via RF channel 32 (e.g.,using 15 MHz of bandwidth, and based on RF channel 32 historically beingassociated with less congestion than other RF channels of the U-NII-1band). In this way, base station 220 reduces interference and improvesthroughput in a high-congestion situation by using an RF channel that isnot likely to be associated with significant congestion, even though thechannel is impaired (due to the ability to only use 15 MHz of thetheoretically available bandwidth of 20 MHz).

Continuing the above example, in a situation where the U-NII-1 band isassociated with a moderate congestion value (e.g., a bandwidthutilization value of, for example, between approximately 25% andapproximately 50%, etc.), base station 220 may select, for example, RFchannel 32 and another selected RF channel of RF channels 36 through 48.Base station 220 may communicate with UEs 210 via RF channel 32 and theother RF channel (e.g., using the 15 MHz of bandwidth associated with RFchannel 32 in addition to the 20 MHz of bandwidth associated with theother RF channel). In some implementations, base station 220 mayallocate a subset of the bandwidth associated with the other RF channel.For example, if the other RF channel is associated with a bandwidthutilization value of 50%, base station 220 may allocate 10 MHz ofbandwidth with regard to the other RF channel (e.g., based on 10 MHz, or50%, of the bandwidth associated with the other RF channel beingutilized). In this way, base station 220 can reduce interference byproviding RF signals via RF channel 32, and can increase throughput byproviding RF signals via the other selected RF channel.

Still continuing the above example, in a situation where the U-NII-1band is associated with a relatively low congestion value (e.g., abandwidth utilization value of, for example, approximately 0% toapproximately 25%), base station 220 may select, for example, two ormore RF channels of RF channels 36 through 48. Base station 220 maycommunicate with UEs 210 via the two or more RF channels (e.g., using atotal bandwidth that is equal to approximately 20 MHz multiplied by aquantity of the two or more RF channels). For example, in a situationwhere base station 220 selects two RF channels that are each associatedwith a bandwidth of 20 MHz and a bandwidth utilization value of 10%,base station 220 may provide a bandwidth of 36 MHz (e.g., based on 90%of the 40 MHz associated with the two RF channels being un-utilized). Inthis way, base station 220 maximizes throughput by avoiding the impairedRF channel 32.

The example described above may be altered in other configurations. Forexample, the thresholds described above for determining the bandwidthutilization levels at which an impaired RF channel may be selected fortransmission may be adjusted, for example, based on the effectivebandwidth of the impaired RF channel available at the base station,measured results of prior threshold assignments on overall congestionand bandwidth utilization, etc.

In some implementations, when base station 220 allocates resources inthe time domain, base station 220 may identify a set of time slotsallocated to a selected RF channel. In this case, base station 220 mayprovide the downlink traffic to UE 210 via the selected RF channel andduring one or more time slots included in the set of time slotsallocated to the selected RF channel. For example, base station 220 mayidentify one or more available time slots included in the set, and mayprovide downlink traffic to UE 210 during the one or more time slots. Insome implementations, base station 220 may perform similar operationswith uplink traffic. For example, base station 220 may provideinformation to UEs 210 identifying one or more time slots available tothe selected RF channel via which the UEs 210 are to transmit uplinkinformation, and may receive uplink traffic from the UEs 210 in the oneor more time slots. In this way, base station 220 reduces interferenceand congestion in the selected RF channel.

As further shown in FIG. 4, process 400 may include communicating withuser equipment via the one or more selected radio frequency channels(block 440). For example, base station 220 may communicate with UE 210via the one or more selected RF channels (e.g., in an uplink direction,in a downlink direction, in an uplink direction and a downlinkdirection, etc.). Base station 220 may provide information, to UE 210,identifying the one or more selected RF channels, frequencies and/orbandwidths associated with the one or more selected RF channels, timeslots associated with the one or more selected RF channels, or the like,and may communicate with UE 210 based on the provided information.

In some implementations, base station 220 may communicate with UE 210via the one or more selected RF channels of the unlicensed RF spectrumband, and via one or more RF channels of a licensed RF spectrum band.For example, base station 220 may use the one or more selected RFchannels for a secondary serving carrier, and may use one or more RFchannels associated with the licensed RF spectrum band for a primaryserving carrier for UE 210 (e.g., based on a license-assisted access(LAA) technology, based on an LTE-Advanced technology, based on an LTE-Utechnology, etc.). In such cases, base station 220 may communicate withUE 210 using the licensed RF spectrum band as an anchor (e.g., to permitUE 210 to camp on base station 220) for UE 210 to connect with basestation 220, and may receive some communications (e.g., uplinkcommunications, downlink communications, a combination of uplinkcommunications and downlink communications, etc.) via the unlicensed RFspectrum band.

In some implementations, base station 220 may communicate with UE 210via the one or more selected RF channels without communicating with UE210 via a licensed RF spectrum band. For example, base station 220 maybroadcast information identifying the one or more selected RF channels,may establish a session with UE 210 via the one or more selected RFchannels, and may communicate with UE 210 via the one or more selectedRF channels. In this way, base station 220 reduces congestion andinterference with regard to the licensed RF spectrum band, whichimproves network efficiency.

Although FIG. 4 shows example blocks of process 400, in someimplementations, process 400 may include additional blocks, fewerblocks, different blocks, or differently arranged blocks than thosedepicted in FIG. 4. Additionally, or alternatively, two or more of theblocks of process 400 may be performed in parallel.

In this way, a base station selects an unlicensed RF spectrum band andallocates RF channels of the selected band based on congestion in theselected band. In some implementations, when a selected band isassociated with high congestion, the base station may allocate animpaired RF channel that is historically associated with lowercongestion than other RF channels in an RF spectrum band, which reducescongestion and interference, and which improves network throughput inhigh-congestion situations.

The foregoing disclosure provides illustration and description, but isnot intended to be exhaustive or to limit the implementations to theprecise form disclosed. Modifications and variations are possible inlight of the above disclosure or may be acquired from practice of theimplementations.

As used herein, the term component is intended to be broadly construedas hardware, firmware, or a combination of hardware and software.

Some implementations are described herein in connection with thresholds.As used herein, satisfying a threshold may refer to a value beinggreater than the threshold, more than the threshold, higher than thethreshold, greater than or equal to the threshold, less than thethreshold, fewer than the threshold, lower than the threshold, less thanor equal to the threshold, equal to the threshold, etc.

To the extent the aforementioned embodiments collect, store, or employpersonal information provided by individuals, it should be understoodthat such information shall be used in accordance with all applicablelaws concerning protection of personal information. Additionally, thecollection, storage, and use of such information may be subject toconsent of the individual to such activity, for example, through wellknown “opt-in” or “opt-out” processes as may be appropriate for thesituation and type of information. Storage and use of personalinformation may be in an appropriately secure manner reflective of thetype of information, for example, through various encryption andanonymization techniques for particularly sensitive information.

It will be apparent that systems and/or methods, described herein, maybe implemented in different forms of hardware, firmware, or acombination of hardware and software. The actual specialized controlhardware or software code used to implement these systems and/or methodsis not limiting of the implementations. Thus, the operation and behaviorof the systems and/or methods were described herein without reference tospecific software code—it being understood that software and hardwarecan be designed to implement the systems and/or methods based on thedescription herein.

Even though particular combinations of features are recited in theclaims and/or disclosed in the specification, these combinations are notintended to limit the disclosure of possible implementations. In fact,many of these features may be combined in ways not specifically recitedin the claims and/or disclosed in the specification. Although eachdependent claim listed below may directly depend on only one claim, thedisclosure of possible implementations includes each dependent claim incombination with every other claim in the claim set.

No element, act, or instruction used herein should be construed ascritical or essential unless explicitly described as such. Also, as usedherein, the articles “a” and “an” are intended to include one or moreitems, and may be used interchangeably with “one or more.” Furthermore,as used herein, the term “set” is intended to include one or more items(e.g., related items, unrelated items, a combination of related andunrelated items, etc.), and may be used interchangeably with “one ormore.” Where only one item is intended, the term “one” or similarlanguage is used. Also, as used herein, the terms “has,” “have,”“having,” or the like are intended to be open-ended terms. Further, thephrase “based on” is intended to mean “based, at least in part, on”unless explicitly stated otherwise.

What is claimed is:
 1. A base station, comprising: a memory; and one ormore processors to: determine an effective bandwidth of an impairedradio frequency (RF) channel, the impaired RF channel located within aband of unlicensed RF spectrum containing multiple channels, theimpaired RF channel being an RF channel that is less congested thanother RF channels in the band of unlicensed RF spectrum containingmultiple channels; obtain channel usage information associated with theband of unlicensed RF spectrum; select one or more RF channels from themultiple channels based on one or more congestion values of the band ofunlicensed RF spectrum and the effective bandwidth of the impaired RFchannel, where the one or more processors, when selecting the one ormore RF channels, are to: select the impaired RF channel as one of theone or more selected RF channels when the one or more congestion valuesare above a threshold,  the threshold being based on the effectivebandwidth of the impaired RF channel; and communicate with userequipment on the one or more selected RF channels.
 2. The base stationof claim 1, where the one or more processors, when obtaining the channelusage information, are to: obtain channel usage information for theimpaired RF channel when a licensed RF spectrum band is associated witha particular congestion level.
 3. The base station of claim 1, where theone or more processors are further to: identify a set of time slotsallocated to one of the one or more selected RF channels, and where theone or more processors, when communicating with the user equipment, areto: communicate with the user equipment based on the set of time slotsallocated to the one of the one or more selected RF channels.
 4. Thebase station of claim 1, where the one or more processors, whenobtaining the channel usage information, are to: obtain channel usageinformation for the impaired RF channel when a licensed RF spectrum bandsatisfies a threshold quantity of user equipment.
 5. The base station ofclaim 1, where the one or more processors are further to: rank each ofthe one or more RF channels based on congestion information; and applyweights corresponding to the ranking of each of the one or more RFchannels, and the one or more processors, when selecting the one or moreRF channels, are to: select the one or more RF channels based onapplying the weights.
 6. The base station of claim 1, where the one ormore processors, when determining the effective bandwidth of theimpaired RF channel, are to: determine the effective bandwidth of theimpaired RF channel based on configuration information associated withthe base station.
 7. A non-transitory computer-readable medium storinginstructions, the instructions comprising: one or more instructionsthat, when executed by one or more processors, cause the one or moreprocessors to: determine an effective bandwidth of an impaired radiofrequency (RF) channel, the impaired RF channel located within a band ofunlicensed RF spectrum containing multiple channels, the impaired RFchannel being an RF channel that is less congested than other RFchannels in the band of unlicensed RF spectrum containing multiplechannels; obtain channel usage information associated with the band ofunlicensed RF spectrum; select one or more RF channels from the multiplechannels based on one or more congestion values of the band ofunlicensed RF spectrum and the effective bandwidth of the impaired RFchannel, where the one or more instructions, that cause the one or moreprocessors to select the one or more RF channels, cause the one or moreprocessors to: select the impaired RF channel as one of the one or moreselected RF channels when the one or more congestion values are above athreshold,  the threshold being based on the effective bandwidth of theimpaired RF channel; and communicate with user equipment on the one ormore selected RF channels.
 8. The non-transitory computer-readablemedium of claim 7, where the one or more instructions, that cause theone or more processors to obtain the channel usage information, causethe one or more processors to: obtain channel usage information for theimpaired RF channel when a licensed RF spectrum band is associated witha particular congestion level.
 9. The non-transitory computer-readablemedium of claim 7, where the one or more instructions that further causethe one or more processors to: identify a set of time slots allocated toone of the one or more selected RF channels, and the one or moreinstructions, that cause the one or more processors to communicate withthe user equipment, cause the one or more processors to: communicatewith the user equipment based on the set of time slots allocated to theone of the one or more selected RF channels.
 10. The non-transitorycomputer-readable medium of claim 7, the one or more instructions, thatcause the one or more processors to determine the effective bandwidth ofthe impaired RF channel, cause the one or more processors to: determinethe effective bandwidth of the impaired RF channel based onconfiguration information associated with a base station.
 11. Thenon-transitory computer-readable medium of claim 7, where the one ormore instructions further cause the one or more processors to: rank eachof the one or more RF channels based on congestion information; andapply weights corresponding to the ranking of each of the one or more RFchannels, and the one or more instructions, that cause the one or moreprocessors to select the one or more RF channels, cause the one or moreprocessors to: select the one or more RF channels based on applying theweights.
 12. The non-transitory computer-readable medium of claim 7, theone or more instructions, that cause the one or more processors toobtain the channel usage information, cause the one or more processorsto: obtain channel usage information for the impaired RF channel when alicensed RF spectrum band satisfies a threshold quantity of userequipment.
 13. A method, comprising: determining, by a base station, aneffective bandwidth of an impaired radio frequency (RF) channel, theimpaired RF channel located within a band of unlicensed RF spectrumcontaining multiple channels, the impaired RF channel being an RFchannel that is less congested than other RF channels in the band ofunlicensed RF spectrum containing multiple channels; obtaining, by thebase station, channel usage information associated with the band ofunlicensed RF spectrum; selecting, by the base station, one or more RFchannels from the multiple channels based on one or more congestionvalues of the band of unlicensed RF spectrum and the effective bandwidthof the impaired RF channel, where selecting the one or more RF channelscomprises: selecting the impaired RF channel as one of the one or moreselected RF channels when the one or more congestion values are above athreshold, the threshold being based on the effective bandwidth of theimpaired RF channel; and communicating, by the base station, with userequipment on the one or more selected RF channels.
 14. The method ofclaim 13, where obtaining the channel usage information comprises:obtaining channel usage information for the impaired RF channel when alicensed RF spectrum band is associated with a particular congestionlevel.
 15. The method of claim 13, further comprising: identifying a setof time slots allocated to one of the one or more selected RF channels,and where communicating with the user equipment comprises: communicatingwith the user equipment based on the set of time slots allocated to theone of the one or more selected RF channels.
 16. The method of claim 13,further comprising: ranking each of the one or more RF channels based oncongestion information; and applying weights corresponding to theranking of each of the one or more RF channels, and where selecting theone or more RF channels comprises: selecting the one or more RF channelsbased on applying the weights.
 17. The method of claim 13, wheredetermining the effective bandwidth of the impaired RF channelcomprises: determining the effective bandwidth of the impaired RFchannel based on configuration information associated with the basestation.
 18. The base station of claim 1, where the channel usageinformation for a given RF channel, of the multiple channels, includesone or more of: a bandwidth utilization value that is determined basedon a ratio of an available bandwidth on the given RF channel to a totalbandwidth of the given RF channel, an interference value identifyinginterference received by the base station in association with the givenRF channel, or a ratio of unallocated time slots on the given RF channelto total time slots on the given RF channel.
 19. The non-transitorycomputer-readable medium of claim 7, where the channel usage informationfor a given RF channel, of the multiple channels, includes one or moreof: a bandwidth utilization value that is determined based on a ratio ofan available bandwidth on the given RF channel to a total bandwidth ofthe given RF channel, or a ratio of unallocated time slots on the givenRF channel to total time slots on the given RF channel.
 20. The methodof claim 13, where the channel usage information for a given RF channel,of the multiple channels, includes one or more of: a bandwidthutilization value that is determined based on a ratio of an availablebandwidth on the given RF channel to a total bandwidth of the given RFchannel, an interference value identifying interference received by thebase station in association with the given RF channel, or a ratio ofunallocated time slots on the given RF channel to total time slots onthe given RF channel.